An electric motor comprises a stator and a rotor. Drive elements of the stator generate varying magnetic fields which cause the rotor to spin about an axis. Such magnetic fields are generated by current flowing through coils in the drive elements. The temperature of the motor in use is related to the magnitude of current flowing through the coils. Each of the materials used within the motor will have a life rated temperature limit for continuous operation. The maximum power output of an electric motor is thus restricted by the temperature limit for one of these materials because above this temperature the service life of this material will be reduced.